523
FXUS65 KBYZ 070120
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
720 PM MDT TUE JUN 6 2023
UPDATE
UPDATED POPS TO REFLECT LATEST RADAR TRENDS. NAM12 SEEMED TO HAVE
A GOOD HANDLE ON THE TRENDS, SO BLENDED POPS WITH THIS MODEL
THROUGH THE NIGHT. POPS QUICKLY TREND DOWN AFTER 06Z. LATEST
RADAR SHOWED SCATTERED SHOWERS AND THUNDERSTORMS, MAINLY OVER
YELLOWSTONE AND NORTHERN BIG HORN COUNTY. A FEW STORMS ALSO
DEVELOPED AS FAR SE AS CARTER COUNTY. LATEST MESOANALYSIS SHOWED
PWAT'S ABOVE 1 INCH OVER MAIN AREA OF STORMS, SO HEAVY RAIN
REMAINS LIKELY AND WILL CONTINUE WITH ANY THUNDERSTORMS OVERNIGHT.
HAVE BEEN COVERING STORM PROGRESSION WITH FFW'S AND SPS'S THIS
EVENING. BESIDES SOME WATER ON ROADS, HAVE HAD PEA-SIZED HAIL
REPORTS AND 2 FUNNEL CLOUD REPORTS THIS EVENING. MESOANALYSIS
SHOWED CIN INCREASING OVER THE WESTERN AND CENTRAL PARTS OF THE
FORECAST AREA THIS EVENING, AND CIN WAS PROJECTED TO INCREASE AND
SPREAD E THROUGH THE REMAINDER OF THE AREA THROUGH THE NIGHT.
SHEAR WAS WEAK. THERE WAS SOME WEAK ENERGY OVER THE AREA WHICH
WILL REMAIN OVER THE REGION INTO WEDNESDAY. WITH PLENTY OF
MOISTURE REMAINING OVER THE AREA, POPS WILL INCREASE AGAIN WED.
AFTERNOON. NO CHANGES TO THE VARIOUS FLOOD WATCHES. ARTHUR
DISCUSSION
THROUGH FRIDAY MORNING...
MAIN THREATS FOR THE SHORT TERM REVOLVE AROUND THE POTENTIAL FOR
ADDITIONAL HEAVY RAIN WITH THUNDERSTORMS OVER THE NEXT FEW DAYS,
AS WELL AS THE FLOWS ON THE MUSSELSHELL RIVER WHICH IS NEAR
BANKFULL FROM SHAWMUT TO LAVINA AT THIS TIME.
NO MAJOR CHANGES TO THE FORECAST PATTERN OVER THE SHORT TERM.
OMEGA BLOCKING PATTERN REMAINS IN PLACE WITH UPPER RIDGE OVER THE
NC PLAINS STATES INTO SC CANADA AND UPPER LOWS OVER CALIFORNIA AND
OVER THE EAST COAST. THIS BLOCK WILL ALLOW FOR GULF OF
MEXICO/PLAINS MOISTURE TO CONTINUE TO BE PUMPED INTO THE AREA OVER
THE NEXT WEEK, KEEPING THE THREAT FOR HEAVY RAIN WITH
SHOWERS/THUNDERSTORMS IN PLAY. THE BEST PERIODS FOR HEAVY
PRECIPITATION IN THE SHORT TERM WILL BE THIS AFTERNOON THROUGH
LATE TONIGHT, AND THEN AGAIN ON THURSDAY. RIDGE FLOPS WESTWARD
SOME ON WEDNESDAY WHICH MAY CAP OFF STORMS TO ISOLATED COVERAGE OVER
THE LOWER ELEVATIONS AS FAR WEST AS BILLINGS AND ROUNDUP,
PROVIDING A BREAK FOR SOME AREAS THAT HAVE SEEN HEAVY RAIN
RECENTLY. HOWEVER ITS CERTAINLY NOT A DRY FORECAST. BY THURSDAY
STORMS BEGIN TO MAKE IT FURTHER EAST INTO SE MONTANA AS THE
CALIFORNIA UPPER LOW PRESSES NORTHEASTWARD INTO THE GREAT BASIN
AND PUSHES A FEW DISTURBANCES OUR WAY. AS THESE DISTURBANCES
ARRIVE THE LOW LEVEL FLOW TURNS EASTERLY ADVECTING IN MORE PLAINS
MOISTURE FOR A FAVORABLE UPSLOPE FLOW INTO THE WESTERN HALF OF
THE AREA, BOOSTING HEAVY PRECIPITATION CHANCES AGAIN.
THUNDERSTORMS WON'T HIT EVERY LOCATION IN THE WATCH TONIGHT, BUT
THOSE AREAS THAT DO GET HIT HAVE A HIGH PROBABILITY FOR FLASH
FLOODING WITH SATURATED GROUND AND VERY HEAVY RAINFALL FROM SLOW
MOVING STORMS. WHERE IT TOOK SEVERAL DAYS TO PRODUCE THE HEAVY
RAIN LAST WEEKEND, IT WILL ONLY TAKE AN HOUR OR TWO TO PRODUCE 1
TO 2+ INCHES OF RAIN WITH THESE STORMS TONIGHT. THE SAME SCENARIO
IS LIKELY WITH STORMS THURSDAY, WITH A LESSOR CHANCE WEDNESDAY AS
DESCRIBED ABOVE.
THUNDERSTORM TIMING FOR BILLINGS AREA...6PM TO 10PM THIS EVENING.
AS NOTED IN THE PREVIOUS DISCUSSION WILL CONTINUE THE FLOOD WATCH
FOR THE MUSSELSHELL RIVER FROM SHAWMUT TO LAVINA UNTIL FURTHER
NOTICE TO ACCOUNT FOR THE NEAR BANKFULL CONDITIONS CURRENTLY, AND
THE POTENTIAL FOR ADDITIONAL PRECIPITATION UPSTREAM THAT MAY PUSH
THE RIVER OVER FLOOD STAGE GOING FORWARD.
WILL MOST LIKELY NEED ADDITIONAL FLOOD/FLASH FLOOD WATCHES FOR
LATER IN THE WEEK (THU/FRI/PSBL SAT). WILL LET THE CURRENT
ITERATION PLAY OUT SO WE DON'T CONFUSE ANYONE ON TIMING AND PUSH
THE DECISION TO THE MIDNIGHT SHIFT TO HANDLE ONCE THE CURRENT
WATCH EXPIRES. CHAMBERS
FRIDAY THROUGH TUESDAY...
OVERALL THE EXTENDED CONTINUES WITH ONLY SOME SMALL SHIFTS IN THE
RAINFALL AMOUNTS, ESPECIALLY THROUGH FRIDAY NIGHT. FRIDAY AND
FRIDAY NIGHT STILL LOOK TO BE POSSIBLE ONE OF THE WETTER PERIODS
IN THE FORECAST AS THE LOW-LEVEL FLOW WILL BE OUT OF THE EAST,
THUS PRODUCING GOOD UPSLOPE, AND STILL VERY MOISTURE RICH. THE
MAIN TAKE AWAY IS THAT CONDITIONS ARE STILL FAVORABLE FOR HEAVY
RAIN ON ALREADY SATURATED SOILS. RUNOFF COULD OCCUR VERY QUICKLY
LEADING TO PONDING OF WATER AND FLOODING OF LOW LYING AREAS.
PRECIPITABLE WATER VALUES WILL REMAIN 1.0 TO 1.2 INCHES. WHILE
THE CHANGES IN THE 24 HOUR TOTAL ENDING AT 6 AM SATURDAY IN THE
NBM MEAN ARE ONLY 0.1 TO 0.2 OF AN INCH, THE UPPER RANGE, 90TH
PERCENTILE, HAS COME UP BY AROUND A HALF INCH FROM YESTERDAY. THE
HEAVIEST AMOUNTS WILL BE FROM BILLINGS WEST TOWARDS THE WESTERN
FOOTHILLS. AMOUNTS ARE STILL GENERALLY IN THE 0.5 TO 1.5 INCH
RANGE. HOWEVER, WITH PLENTY OF CONVECTIVE ENERGY, SIGNIFICANTLY
HIGHER LOCALIZED RAIN AMOUNTS ARE POSSIBLE.
SATURDAY ONWARD, THE PRECIPITABLE WATER VALUES WILL DROP BELOW AN
INCH, THOUGH STAYING ABOVE 0.8 OF AN INCH. ALSO THE RIDGE TO THE
EAST WILL FINALLY START TO BREAK DOWN AS A WAVE MOVES THROUGH
CANADA. WITH THE FLOW PATTERN DISRUPTED SOME THE ACTIVITY WILL NOT
BE A WIDESPREAD, MAINLY FOCUS IN THE HIGHER TERRAIN, AND WITH NOT
BE AS PRODUCTIVE WITH RAIN AMOUNTS. REIMER
AVIATION
SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WITH HEAVY RAIN
AND POSSIBLE PEA-SIZED HAIL WILL CONTINUE OVER MUCH OF THE AREA
THROUGH 06Z, THE DIMINISH QUICKLY AFTER 06Z. MVFR/IFR OR LOWER
CONDITIONS ARE EXPECTED WITH THE PRECIPITATION. THESE CONDITIONS
WILL CONTINUE OVER PARTS OF THE AREA OVERNIGHT DUE TO LOW CLOUDS
AND PATCHY FOG. SHOWERS AND THUNDERSTORMS WILL INCREASE OVER THE
AREA FROM LATE MORNING THROUGH THE AFTERNOON ON WEDNESDAY,
ESPECIALLY FROM AROUND KBIL W, WITH MVFR/IFR OR LOWER CONDITIONS.
EXPECT AREAS OF MOUNTAIN OBSCURATION THROUGH 06Z, THEN INCREASING
MOUNTAIN OBSCURATION AGAIN DURING WEDNESDAY. ARTHUR
PRELIMINARY POINT TEMP/POPS
WED THU FRI SAT SUN MON TUE
-----------------------------------------------------------
BIL 058/081 059/082 058/079 059/072 056/076 056/077 057/076
84/T 57/T 67/T 78/T 44/T 25/T 46/T
LVM 053/079 054/078 053/077 054/075 054/073 052/074 052/073
46/T 59/T 77/T 57/T 57/T 38/T 57/T
HDN 058/083 059/085 058/081 059/075 055/079 055/080 055/077
44/T 45/T 58/T 78/T 33/T 14/T 46/T
MLS 063/088 064/089 064/084 061/077 056/082 058/083 059/081
21/U 34/T 47/T 75/T 11/U 12/T 34/T
4BQ 060/087 061/087 061/084 059/073 053/077 056/080 056/080
32/T 34/T 48/T 77/T 22/W 12/T 35/T
BHK 059/089 060/088 060/083 056/075 049/078 052/082 056/082
11/U 13/T 46/T 63/W 10/U 01/U 23/T
SHR 054/080 054/082 054/079 054/071 051/074 051/077 051/074
25/T 56/T 57/T 58/T 44/T 14/T 36/T
BYZ WATCHES/WARNINGS/ADVISORIES
MT...FLOOD WATCH IN EFFECT UNTIL 3 AM MDT WEDNESDAY FOR ZONES
29-34-42-56-63-66-68-141-170-172-228-235.
WY...NONE.
WEATHER.GOV/BILLINGS
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page